Display devices are commonly characterized in terms of their spatial resolution, their dynamic range and their color range. In addition, there are several other important aspects of a display system that contribute to the realism of the presented image, for example artifacts stemming from a limited refresh rate, suppression of reflection of ambient light sources, and problems due to the fact that displays generally produce two-dimensional projections of three-dimensional objects. The visual acuity of the human eye exceeds the capability of conventional displays in all of these measures, and as such poses a tough challenge for display technologies aimed at photo realistic image and movie reproduction.
For example, standard cathode ray tube (CRT) displays fail to reach their 72 dpi ratings. The limited video bandwidth and large electron spot size in CRT's lead to much lower actual resolution. LCD display panels can reach their rated spatial resolutions, but doubling resolution it is problematic because smaller thin film transistors for each pixel limit the light output possible.
The human eye can adapt to a very wide range of lighting conditions. The range of interest for display devices is the lower part of photopic vision range, which provides good color perception and good spatial resolution. Because of the long time constants involved with adaptation, the simultaneous dynamic range of the human eye defines the desirable dynamic range of a display device, which is about 3.5 orders of magnitude.
Conventional displays feature a relatively small dynamic range. For example, the dynamic range of a typical CRT display is limited by many factors, including the limited bandwidth of the video drivers, optical reflections in the front faceplate, large electron spot size, and scattering from the shadow mask, for example. Projection systems suffer from the fact that the required objective lens itself has a limited dynamic range due to imperfect anti-reflection coatings. The net result is that most display systems achieve, at most, about two orders of magnitude less than what would be required to match the human eye.
Practical color display devices pick a set of three primary colors—red, green and blue—and are limited to reproducing the colors within a triangle defined by the color coordinates of these primary colors. The selection of the primary colors of a display device is subject to many technical limitations. For example, it is difficult to generate monochromatic light efficiently. If a white light source is used for the display, narrow band filters would waste a lot of light, hence projection and LCD displays tend to use primary colors quite far from the spectral boundary of human vision. Another factor concerning the primary blue and red colors is the diminishing sensitivity of the eye toward the end of the visible wavelength range.
In at least preferred embodiments, the present invention seeks to provide a surround-vision display system having one or more of improved spatial resolution, dynamic range, and color range than prior art display systems and circuitry suitable for use in such a surround-vision display system.